Campylobacter pylori (C. pylori) was first isolated in 1982. It is now known to be an important cause of gastritis and has been associated with duodenal ulcer, gastric ulcer, dyspepsia and gastric carcinoma. Since the discovery in 1982 there has been a tremendous worldwide interest in C. pylori and in trying to delineate its actual role in gastric disease and the formation of ulcers. Despite the numerous studies showing a close association between C. pylori and abnormal gastric pathology, there is insufficient evidence to determine conclusively whether the organism is pathogenic or opportunistic. Nevertheless, the presence of C. pylori is an important consideration in treating gastric disease.
Patients colonized with C. pylori elicit a specific antibody response which is potentially useful as a diagnostic aid and for monitoring the disease state during treatment. Consequently, many systems have been developed to detect serum anti C. pylori antibodies. However, preliminary studies suggest that C. pylori displays antigenic cross-reactivity with the thermophilic campylobacteria C. jejuni and C. coli. This cross-activity results in lack of specificity.
In attempts to avoid the problems associated with cross-reactivity, investigators have extensively studied the acid extractable surface proteins and outer membrane proteins of C. pylori. Newall, D. G., Journal of General Microbiology 133:163-170 (1987); and Perez-Perez, G. I. and Blaser, M. J., Infection and Immunity 55:1256-1263 (1987). Newall demonstrated that there existed acid extractable proteins in the molecular range of 20,000 to some of these proteins were similar to proteins of C. jejuni and many also showed cross-reactivity with C. jejuni. At least one major antigen (approximately 60,000 daltons) showed only minimum cross-reactivity with C. jejuni, however, there still was some cross-reactivity. On the other hand, Perez-Perez showed that an antigen of about 62,000 daltons had significant cross-reactivity. C. pylori is capable of elicting both a systemic and local antibody response in patients with chronic gastritis, however, this secretory-antibody response does not appear to eliminate the colonization. Rathbone, B. J. et al., Gut, 27:642-647 (1986). Rathbone et al used the whole organism in their immunological assay.
Other studies using the immunoblot technique show that C. pylori has a number of immuno-reactive components in the range of 100,000 daltons or less. Kaldor, J. et al. The Medical Journal of Australia 145:133-135 (1986).
Whole organism ELISA assays detect C. pylori antibody but still are unable to solve the cross-reactivity problem. Morris et al. The New Zealand Medical Journal 99:657-659 (1986).
Acid-glycine extracts of C. pylori detect antibodies using ELISA techniques. However, a number of false positives and false negatives exist. Although the relative number of each false result can be regulated by adjusting the cut off point, there is still significant overlap between the groups. Goodwin et al. The Journal of Infectious Disease 155:488-494 (1987). Similar results are found using complement fixation, bacterial aglutination and immunoblotting. Jones et al. General Clinical Pathology 37:1002-1006 (1984) and Jones et al. J. of Ed. Microbiology 22:57-62 (1986). Acid washed fractions show similar results in both complement fixation and SDS-PAGE immunoblots. Wulffen et al. Journal of Clinical Microbiology 24:716-720 (1986).
Numerous reports exist showing C. pylori antibodies in the serum of affected humans. All of the studies have dealt with the outside surface of the microorganism. In these test systems, the antigen is either the whole organism or sub parts of the flaggella and outside membrane in the molecular weight range of about 100,000 daltons or less. None of these studies are adequate to allow accurate detection of the infection. There is significant misclassification, both false positive and false negative, as well as significant cross-reactivity with other organisms, such as C. jejuni and C. coli. Thus, there exists a need for a quick immunological method to specifically detect the C. pylori antibody. The present invention meets this need. The present invention describes a new and accurate serological assay for the diagnosis of C. pylori infection. Previously published results used lower molecular weight compounds and had significant levels of cross-reactivity with other bacteria. No other assay has the same overall reliability (sensitivity plus specificity).
The symptom dyspepsia is associated with large health care expenditures throughout the western world. Although accurate statistics as to the frequency of dyspepsia are difficult to obtain, recent studies have shown it to be a common problem. In England, for example, it has been estimated that approximately 1% of patients served by general practitioners will present each year with the primary complaint of dyspepsia. The costs of dyspepsia are many and include: (i) those for drugs such as antacids or H.sub.2 -receptor antagonists (sales of cimetidine and ranitidine were more than 2 billion dollars); (ii) charges for diagnostic evaluations such as barium upper gastrointestinal series or fiberoptic endoscopy and (iii) costs associated with time off from work. The effects of dyspepsia on drug use were studied by evaluating patients in Sweden in whom a clinical diagnosis of gastritis or non-ulcer dyspepsia was made. Tyllstrom et al. Scand. J Gastroenterol 1984, 19:755-60.
Tyllstrom found that antacid or H.sub.2 -receptor antagonist therapy was common among these patients. In fact, most patients who visited a physician were given a prescription. This result is similar to data from Britain in which 91% of such patients reported regular use of antacids. Tyllstrom calculated that 1% of the entire population of Sweden was taking a daily dose and that non-ulcer dyspepsia was a primary indication for cimetidine use, accounting for 35% of the prescriptions. There was also noted an increasing trend in the percentage of patients treated with cimetidine.
Because of the high incidence and cost of gastric problems and ulcers in western society, the ability to detect and monitor the treatment of these diseases is highly desirable. Thus the present invention is important in its ability to specifically detect C. pylori which is associated with these diseases and whose disappearance is associated with clinical improvement.